The way i solo tame a rex of any level is to have a flying mount and enough tranq darts or arrows for the Rex in question, Agro the Rex and land away from it so it walks towards you, jump off your mount and shoot it in the head as it does this, fly over its head or around it and repeat, be fast!
I recommend using a scorpion to tame it, pump all levels into health on the scorpion. Then just attack the Rex but with 10 to 20 seconds in between hits, DO NOT pump anything into dm. Also this is what I use to tame literally everything, and it doesn’t even cost anything. Pls put this up in chat for everyone to go “oh that’s not a bad idea” 👌😄👍
If you use the bear trap strategy which is if you lead it into a Dino gateway that is shaped in a triangle and with a bear trap in the middle (Large Beartrap) and when it is stuck you must put a dinogate behind it to trap it and then knock out.
The way I tamed one: place a stone pillar, then on that one another then on that one another until you have a ten tall pillar thing, then one stone ceiling on the very top pillar. around that stone ceiling make a 3x3 stone ceiling thingy. I have one near the red woods for Rex's around that area. When a rex near tower camp thing ,tranq(when fleas, you must have good aim)if successful it will get knocked out obviously🤓 Then just feed (Bring cryopod as usual)